1. Field of the Invention
The present invention relates to an electronic circuit which is used in a digital circuit to prevent the passage of pulses having a pulse width narrower than a predetermined value.
2. Description of the Prior Art
In accordance with recent progress in the development of electronic computers, rapid operation is required for a digital circuit, such as memory, which is used in an electronic computer. For the purpose of operating the memory at ultra high speed, the time which is required for selecting an address of the memory, writing information into the memory or reading the information from the memory must be reduced. Therefore, pulses which have a very narrow pulse width, such as for example several nanoseconds, and high speed digital circuits responsive to such pulses are used in recent electronic computers.
When very high speed digital circuits responsive to very narrow signal pulses are used for an electronic computer, the pulse width of the pulses used in the computer approaches that of noise caused by crosstalk in the computer. A minimum pulse width of signal pulses may be selected so that all elements of the digital circuits to which the signal pulses are supplied can be actuated only by pulses having the minimum pulse width. Sensitivities of the elements cannot be made uniform even if all of the elements are formed in an integrated circuit, and some of them are actuated by a pulse having a width narrower than the minimum pulse width. Such unevenness of sensitivities of electronic elements is particularly serious in integrated semiconductor memory devices, and it is therefore desired to avoid such uneven actuation. When noise having a very narrow pulse width is applied to the digital circuits, some elements of the digital circuits may be actuated and the operation of the digital circuits may be disturbed, so that a malfunction may be caused. In the integrated semiconductor memory devices, such a malfunction is apt to happen in the period of a write cycle, because sensitivities of memory cells of the device to write pulses are not uniform. Thus, false information may be written into some of the memory cells by an external noise pulse having a very narrow width.